Atom interferometry provides a useful tool for precision measurements in geodesy, inertial navigation, and fundamental physics. In light-pulse atom interferometers, stimulated Raman transitions commonly provide the atom optics that coherently split, reflect, and recombine atom wavepackets. U.S. Pat. Nos. 5,274,231 and 5,274,232, each of which is herein incorporated by reference in its entirety, disclose examples of methods and apparatus for manipulating quantum objects, such as atoms, using stimulated Raman transitions. The conventional Raman beamsplitter implementation, which uses resonant pulses to drive atomic transitions, is sensitive to variations in the intensity and difference frequency of the Raman optical fields. These variations can be minimized in a laboratory setting, but will be unavoidably larger in dynamic environments, degrading the performance of practical sensors. In addition, Raman pulses are limited in the thermal velocity range of atoms that can be effectively addressed.
Adiabatic rapid passage (ARP; also known as adiabatic fast passage (AFP)) is a technique used in nuclear magnetic resonance (NMR) to produce rotation of the macroscopic magnetization vector by shifting the frequency of radio frequency (RF) energy pulses (or the strength of the magnetic field) through resonance (the Larmor frequency) in a time that is short compared to the relaxation times. Rather than applying an RF tipping field of fixed orientation and magnitude orthogonal to the holding magnetic field, a field of variable direction is initially applied parallel to an initial polarization and swept into the desired orientation. The polarization is “dragged” while preserving its relative orientation angle with the RF field if the sweep occurs on a timescale much longer than a period of precession about the RF field. One method of varying the RF tipping field direction is by sweeping the RF frequency, as discussed, for example, in U.S. Pat. No. 4,695,799. U.S. Pat. No. 4,695,799 discloses various frequency sweep regimens in the context of NMR.
An optical beamsplitter method using adiabatic rapid passage is discussed in Atomic interferometer based on adiabatic population transfer, Weitz et al., Phys. Rev. Lett. Vol. 73, pp 2563-2566 (1994), and in Precision atom interferometry with light pulses, B. Young et al., in Atom Interferometry, ed. P. Berman (Academic Press, 1996), p. 363. In this method, a pair of laser beams with a fixed laser frequency difference, but having variable laser beam power, was used to achieve atomic population transfer.